Short version:
Biological evolution is an observable process by which populations of organisms change over time. The phrase "change in allele frequencies over time" refers to the changes in gene variations over time in said populations.
The Theory of Evolution is the body of scientific knowledge that seeks to explain this process we observe. It includes descriptions of both the mechanisms of the process and descriptions of the natural history of life on Earth as shaped by the same process.
Longer version:
The process of evolution is the same now as in the past
The process of evolution over time hasn't changed. As long as you have populations of organisms that reproduce, the process of evolution will always continue.
Evolution occurs in populations
Since evolution is a change in populations over time, evolution takes place at the population, not individual level.
All modern organisms are equally "evolved"; evolution has no "levels"
There are no levels to evolution. There is no ladder of evolutionary progress by which organisms are predestined to evolve through.
Rather, all modern organisms are equally evolved. The only real measure in this context is time. And since all lineages go back to the same starting point, all organisms are effectively equal in that respect.
Evolution is like a recursive process
I conceptualize the process of evolution as similar to a recursive process. Essentially the output of one generation becomes the input of the next. Thus there is no real starting point or baseline when talking about the process (save for the origin of life itself). The baseline is constantly changing.
I also recognize that all of the biological categories we assign to organisms are strictly artificial. Species designations and other taxonomical assignments are human invented categories. We do it because it makes organisms easier to talk about. But the actual organisms are not biologically confined to a particular "type" or category in that manner.
I think this represents a fundamental difference with how creationists conceptualize biology and the process of evolution. Creationists seem to conceptualize organisms as having these fixed types and therefore organisms are confined to these types in the context of the process of evolution. However, these types do not exist in nature (which is why you can never get a consistent definition of "kind" from creationists).
Evolution produces genetic information
The process of evolution is constantly producing new genetic information. Studying the process at the molecular level reveals that virtually every type of change to genomes, including the production of novel protein functions is possible. By any definition of information as applicable to genetics, it's demonstrable that evolution produces genetic information through variation during reproduction.
Evolution produces complexity
Evolution produces complexity through functional dependence. This especially seems to be the case with functional specialization that can occur through loss of function. E.g. if you have a multi-functional protein with redundancy, removal of that redundancy creationists greater functional dependence. Learning about protein function and how proteins can serve multiple purposes was a revelation in understanding evolution of complexity. Similarly with functional organs, since many organs serve multiple purposes. Studying the history of organ evolution shows how functions can change and become more specialized over time.
